Metal nitrosyl complexes of bioinorganic, catalytic, and environmental relevance: A novel single-step synthesis of dinitrosylmolybdenum(0) complexes of {Mo(NO)2}6 electron configuration involving Schiff bases derived from 4-acyl-3-methyl-1-phenyl-2-pyrazolin-5-one and 4-aminoantipyrine, directly from molybdate(VI) and their characterization

Article abstract of DOI:10.1016/j.molstruc.2006.03.094

This paper reports the synthesis of five new hexa-coordinated mixed-ligand dinitrosyl complexes of molybdenum(0) of the composition [Mo(NO)₂(L)(OH)], where LH = N-(3′-methyl-1′-phenyl-4′-valerylidene-2′-pyrazolin-5′-one)-4-aminoantipyrine (mphvp-aapH), N-(4′-benzoylidene-3′-methyl-1′-phenyl-2 ′-pyrazolin-5′-one)-4-aminoantipyrine (bmphp-aapH), N-(3′-methyl-1′-phenyl-4′-propionylidene-2′-pyrazolin-5′-one)-4-aminoantipyrine (mphpp-aapH), N-(4′-acetylidene-3′-methyl-1′-phenyl-2′-pyrazolin-5 ′-one)-4-aminoantipyrine (amphp-aapH) or N-(-4′-iso-butyrylidene-3′-methyl-1′-phenyl-2′-pyrazolin-5′-one)-4-aminoantipyrine (iso-bumphp-aapH) directly from molybdate (VI) in a single step and in a single pot. The compounds so obtained have been characterized by elemental analyses, molar conductance, decomposition temperature and magnetic measurements, thermogravimetric analyses, infrared and electronic spectral studies. They were found to contain low-spin [Mo(NO)₂]⁶ electron configuration. A cis-octahedral structure has been proposed for these complexes. The 3D molecular modeling and analysis for bond lengths and bond angles have also been carried out for one of the representative compounds, [Mo(NO)₂(bmphp-aap)(OH)] (2).

Full text of DOI:10.1016/j.molstruc.2006.03.094

Journal of Molecular Structure 798 (2006) 89–101
www.elsevier.com/locate/molstruc
Metal nitrosyl complexes of bioinorganic, catalytic, and environmental
relevance: A novel single-step synthesis of dinitrosylmolybdenum(0)
complexes of {Mo(NO)2}6 electron configuration involving Schiff
bases derived from 4-acyl-3-methyl-1-phenyl-2-pyrazolin-5-one
and 4-aminoantipyrine, directly from molybdate(VI)
q
and their characterization
*
R.C. Maurya , A. Pandey, J. Chaurasia, H. Martin
Coordination and Bioinorganic Chemistry Laboratory, Department of P.G. Studies and Research in Chemistry, R.D. University, Jabalpur 482 001, India
Received 17 October 2005; received in revised form 16 March 2006; accepted 20 March 2006
Available online 2 June 2006
Abstract
This paper reports the synthesis of five new hexa-coordinated mixed-ligand dinitrosyl complexes of molybdenum(0) of the composi-
tion [Mo(NO)2(L)(OH)], where LH = N-(30-methyl-10-phenyl-40-valerylidene-20-pyrazolin-50-one)-4-aminoantipyrine (mphvp-aapH),
0
N-(40-benzoylidene-30-methyl-10-phenyl-2 -pyrazolin-50-one)-4-aminoantipyrine (bmphp-aapH), N-(30-methyl-10-phenyl-40-propionylid-
0
ene-20-pyrazolin-50-one)-4-aminoantipyrine (mphpp-aapH), N-(40-acetylidene-30-methyl-10-phenyl-20-pyrazolin-5 -one)-4-aminoantipy-
rine (amphp-aapH) or N-(-40-iso-butyrylidene-30-methyl-10-phenyl-20-pyrazolin-50-one)-4-aminoantipyrine (iso-bumphp-aapH) directly
from molybdate (VI) in a single step and in a single pot. The compounds so obtained have been characterized by elemental analyses,
molar conductance, decomposition temperature and magnetic measurements, thermogravimetric analyses, infrared and electronic spec-
tral studies. They were found to contain low-spin [Mo(NO)2]6 electron configuration. A cis-octahedral structure has been proposed for
these complexes. The 3D molecular modeling and analysis for bond lengths and bond angles have also been carried out for one of the
representative compounds, [Mo(NO)2(bmphp-aap)(OH)] (2).
ꢀ 2006 Published by Elsevier B.V.
Keywords: Dinitrosylmolybdenum(0) complexes; Pyrazolone based ligands; Bioinorganic; Catalytic; Environmental relevance; 3D molecular modeling
1. Introduction
much attention due to their applications including biologi-
cal, clinical, analytical and pharmacological areas. Even
though 4-aminoantipyrine itself exhibits antimicrobial activ-
ity [2], it has reported to be enhanced due to the condensation
with aldehydes, ketones, thiosemicarbazides, carbazides,
etc.
The Schiff base derivatives [1] of 4-aminoantipyrine (4-
amino-2,3-dimethyl-1-phenyl-2-pyrazolin-5-one) received
q
Enemark and Feltham have proposed circumventing the problem of
The nitrosyl group’s ability to bind to transition met-
als in a linear or a bent fashion [3–6], to behave as
NO+ or NOꢀ [6,7] and to influence, as well as be influ-
enced by, other ligands in the coordination environment
[8–20] has been of interest to coordination chemists and
theoretical chemists for decades [21–23]. Catalytic appli-
cations [24–29] of transition metal nitrosyl complexes
the nature of the nitrosyl ligand by considering metal nitrosyls as
containing an {M(NO)x}n group, where n is the number of electrons of M,
plus the number of electrons in p*-orbital of NO (or more conveniently, n
is the number of d-electrons if nitrosyl is regarded as being coordinated as
NO+). See Ref. [3].
Corresponding author. Fax: +91 761 2392120.
E-mail addresses: rcmauryajb@dataone.in, rcmaurya@sancharnet.in
(R.C. Maurya).
*
0022-2860/$ - see front matter ꢀ 2006 Published by Elsevier B.V.
doi:10.1016/j.molstruc.2006.03.094

90
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
are of current interest to organometallic and organic
chemists.
[46–48] and [Mo(NO)2(acac)2] (acacH = acetylacetone)
[49,50] as precursors8–12 have been carried out in our
laboratory. Maurya et al. [51] have recently reported the
synthesis and characterization of some dinitrosylmolybde-
num(0) complexes involving 4-butyryl-3-methyl-1-phenyl-
2-pyrazolin-5-one and its Schiff bases with o-phenetidine,
p-ansidine, o-phenylenediamine and m-phenylenediamine,
for the first time, using [Mo(NO)2]2+ moiety [43] as
precursor. The ligational behaviour of 8-hydroxysulphona-
mides [20] towards [Mo(NO)2]2+ has also been examined
by Maurya et al.
In view of the diverse and important applications of tran-
sition metal nitrosyl compounds, and also extending the
search for new dinitrosylmolybdenum(0) complexes, we
have studied the reactivity of [Mo(NO)2]2+ (generated by
the method of Sarkar and Subramanian, Ref. [43]) towards
some Schiff bases derived from pyrazolone based carbonyl
compounds and amine of the same family, not reported
hitherto. Some dinitrosylmolybdenum(0) complexes of the
Schiff bases, such as, N-(30-methyl-10-phenyl-40-valerylid-
ene-20-pyrazolin-50-one)-4-aminoantipyrine (mphvp-aap H),
N-(40-benzoylidene-30-methyl-10-phenyl-20-pyrazolin-50-one)-4-
aminoantipyrine (bmphp-aapH), N-(30-methyl-10-phenyl-
40-propionylidene-20-pyrazolin-50-one)-4-aminoantipyrine
(mphpp-aapH), N-(40-acetylidene-30-methyl-10-phenyl-20-
pyrazolin-50-one)-4-aminoantipyrine (amphp-aapH) or
N-(-40-iso-butyrylidene-30-methyl-10-phenyl-20-pyrazolin-5-
one)-4-aminoantipyrine (iso-bumphp-aapH), have thus
been isolated directly from ammonium heptamolybdate in
a single-step process and the results of our investigation
are reported here.
The recent surge of investigations to the chemistry of
transition metal nitrosyls by inorganic biochemists and
biologists is largely due to the Nobel Prize winning discov-
ery [30–33] that endothelium-derived relaxing factor is the
nitric oxide and to the realization that nitric oxide is impli-
cated in a multitude of physiological and pathophysiologi-
cal functions. Nitric oxide has been shown to have many
bioregulatory functions [34] in mammalian including car-
diovascular control, neuronal signaling and an agent for
defense mechanism against microorganism and tumours.
As a result of these diverse and important applications
many books, reviews and special topic papers are devoted
to transition metal nitrosyl chemistry [35].
The dinitrosyl compounds of molybdenum have gained
considerable interest due to their applicability as homoge-
neous catalysts [36–38]. Some dinitrosylmolybdenum(0)
complexes were reported [29] to be used as catalysts in
isomerization reactions of alkenes. Certain dinitrosyl com-
plexes [29] of transition metals were found to catalyze the
conversion of CO and NO to the less harmful gases CO2
and N2O, which is of intrinsic interest because of their envi-
ronmental relevance. It is recently reported by Keller and
Matusiak [39] that [Mo(NO)2(OCR)2 – Lewis acid] cata-
lysts (Lewis acid = TiCl4, SnCl4, EtAlCl2; R = phenyl,
methylvaleric, ethylhexanoic) induce monosubstituted
acetylenes (phenylacetylene, tert-butylacetylene) to poly-
merize. The catalytic ability of these catalysts strongly
depends on the Lewis acid and solvent.
The widely applied routes to prepare dinitrosylmolybde-
num(0) complexes are: (i) the reactions of [{Mo(NO)2X2}n]
(X = halogens) with ligands [40] and (ii) the reactions of
nitrosyl halides with molybdenum hexacarbonyl or its
derivatives [41]. Bencze et al. [42] have generated dini-
trosylmolybdenum(0) species by the reductive reaction of
nitric oxide with molybdenum pentachloride. The genera-
tion of dinitrosylmolybdenum(0), [Mo(NO)2]2+ moiety,
from ammonium heptamolybdate in aqueous-aerobic con-
ditions [in slightly basic medium (dimethylformamide)] and
its stabilization using mono- and bidentate ligands has
been reported by Sarkar and Subramanian [43]. Following
the method of Sarkar and Subramanian, Perpinan et al.
[44] carried out the reaction of the [Mo(NO)2]2+
moiety with X,Y-donor (mixed coordination sites)
ligands (X,Y = dithiocarbamates, xanthates, 2-picolinate,
o-aminophenoxide, o-aminothiophenoxide or dithizone),
which led to the formation of complexes of the
type [Mo(NO)2(X,Y)2]. Complexes of the type [Mo(NO)2
(HA)2], where H2A = benzohydroxamic acid or salicyl-
hydroxamic acid, have been isolated and characterized by
Bag and co-workers [45]. The complexes have been pre-
pared by reductive nitrosylation of ammonium heptamo-
lybdate by hydroxylamine hydrochloride in the presence
of H2A under aqueous-aerobic conditions.
2. Experimental
2.1. Materials
Ammonium heptamolybdate tetrahydrate (Aldrich
chemical Co., USA), hydroxylamine hydrochloride (Sisco
Chem. Pvt. Ltd, Mumbai), 4-aminoantipyrine (BDH
Chemicals, Mumbai), valeryl chloride, iso-butyryl chloride
(Fluka Chemie, Switzerland), 3-methyl-1-phenyl-2-pyrozo-
line-5-one (Johnson Chemical Co., Bombay), benzoyl chlo-
ride, acetyl chloride and propionyl chloride (Thomas Baker
Chemicals. Ltd, Mumbai) were used as supplied. All other
chemicals used were of AR Grade.
2.2. Preparation of 4-acyl-3-methyl-1-phenyl-2-pyrazolin-
5-one (pyrazolone based carbonyl compounds)
4-Benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (bmphp)
was prepared by the interaction of 3-methyl-1-phenyl-2-
pyrozoline-5-one in dioxane with calcium hydroxide and
benzoyl chloride by the procedure reported by Jensen [52]
and was recrystallised from a methanol–water (9:1) mix-
ture. Analytical data calculated for C17H14N2O2:
C = 73.35%, H = 5.07%, N = 10.06%, Found: C = 73.
56%, H = 5.20%, N = 10.03%. IR data: m(C@O)
The synthesis and characterization of several dini-
trosylmolybdenum(0) complexes using [Mo(NO)2(CN)4]2ꢀ

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
91
(side chain) 1645 cmꢀ1, m(C@O) (ring) 1600 cmꢀ1, m(C@N)
(pyrazolone ring) 1566 cmꢀ1 1H NMR data: d 7.32–
.
7.96 ppm (M, 10H, aromatic), d 2.60 ppm (S, 1H, ACH),
d 1.50 ppm (S, 3H, ACH3). Following the same procedure,
3-methyl-1-phenyl-4-valeryl-2-pyrazolin-5-one
(mphvp),
3-methyl-1-phenyl-4-propionyl-2-pyrazolin-5-one (mphpp),
4-acetyl-3-methyl-1-phenyl-2-pyrazolin-5-one (amphp) and
4-iso-butyryl-3-methyl-1-phenyl-4-pyrazolin-5-one (iso-bumphp)
were prepared using valeryl chloride, propionyl chloride,
acetyl chloride and iso-butyryl chloride, respectively. The
reaction scheme related to the synthesis of 4-acyl-3-meth-
yl-1-phenyl-2-pyrazolin-5-one is as follows:
N
O
Dioxane
Reflux
N
[Ca-complex]
+ Ca(OH)2 + RCOCl
3-Methyl-1-phenyl-2-pyrazolin-5-one
R
O
R = C4H9
(mphvp)
HCl
N
[Ca-complex]
= C6H5
= C2H5
= CH3
(bmphp)
(mphpp)
(amphp)
O
N
= CH(CH3)2 (iso-bumphp)
4-Acyl-3-methyl-1-phenyl-2-pyrazolin-5-one
2.3. Preparation of Schiff base ligands
The Schiff base ligands were prepared [53] by taking 1:1
ethanolic solution of mphvp (2.58 g, 10 mmol), bmphp
(2.78 g, 10 mmol), mphpp (2.30 g, 10 mmol), amphp
(2.16 g, 10 mmol) or iso-bumphp (2.44 g, 10 mmol) and
4-aminoantipyrine (2.03 g, 10 mmol) and refluxing the
resulting solution for 5–7 h. The reaction mixture was then
poured into distilled water (250 mL) when a yellow precip-
itate was obtained. It was filtered, washed several times
with water and then dried in vacuo. The characterization
data of the Schiff base ligands are given in Table 1.
2.4. Synthesis of dinitrosylmolybdenum(0) complexes
Ammonium
heptamolybdate
tetrahydrate
(1 g,
0.8 mmol) and hydroxylamine hydrochloride (1.7 g,
24.4 mmol) were heated in 10 mL DMF at 90 ꢁC for 1 h
to produce a green solution [43]. Into this green solution
was added a solution of mphvp-aapH (2.215 g, 5 mmol),
bmphp-aapH (2.315 g, 5 mmol), mphpp-aapH (2.075 g,
5 mmol), amphp-aapH (2.005 g, 5 mmol) or iso-bumphp-
aapH (2.145 g, 5 mmol) in ꢁ40 mL ethanol. The resulting
solution was refluxed for 8–10 h. The solution was
concentrated on a water bath and kept overnight, when
coloured solid was obtained. It was filtered by suction
and washed several times with 1:5 ethanol water and then

92
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
dried in vacuo. The analytical data of complexes are given
in Table 2.
2.5. Analyses
Carbon, hydrogen and nitrogen were determined micro-
analytically on Heraeus Carlo Erba 1108 elemental analyz-
er. The molybdenum content in each of the synthesized
complexes was determined gravimetrically as MoO2(-
C9H6ON)2 by the method reported elsewhere [54].
2.6. Chemical identification of the coordinated nitrosyl group
The identification of the coordinated nitrosyl group in
the resulting complexes was made by the chemical method
reported by Maurya [6]. Each nitrosyl compound under the
present investigation was decomposed with KOH followed
by acidifying with acetic acid. The resulting filtrate was
added with few drops of the Griess Reagent [55]. The
appearance of a pink colour indicated the coordination
of nitric oxide as NO+ in the complex. The principle
involved in this method is the use of the electrophilic
behaviour of the coordinated NO group in the metal
nitrosyls. The linearly bonded MANAO group may be
assumed to contain ‘‘NO+’’ which can react with strong
ꢀ
alkali to produce NO2
.
2NOþ þ 4OHꢀ ! 2NOꢀ þ 2H2O
2
The resulting NO2ꢀ gives a pink colour [55] with the Griess
reagent.
2.7. Physical methods
Electronic spectra of the complexes were recorded in
dimethylformamide on an ATI Unicam UV-1-100 UV–vis-
ible spectrometer in our laboratory. Magnetic measure-
ments were performed by vibrating sample magnetometer
method at RSIC, IIT, Chennai. Solid state infrared spectra
were obtained using Perkin-Elmer model 1620 FT-IR Spec-
trometer on KBr disc at CDRI, Lucknow. Conductance
measurements were made at room temperatures in dimeth-
ylformamide using a Toshniwal conductivity bridge and
dip-type cell with a smooth platinum electrode of cell con-
stant 1.02. Decomposition temperatures of the Schiff bases
and the chelates were recorded using an electrothermal
apparatus having the capacity to record temperatures up
to 360 ꢁC. Thermogravimetric curves of the complexes
were recorded in the temperature range 50–1000 ꢁC at the
heating rate of 15 ꢁC/min. using a Mettler Toledo Stare
System at the Regional Sophisticated Instrumentation
Centre, Nagpur.
2.8. Molecular modeling studies
The 3D molecular modeling of a representative com-
pound was carried out on a CS Chem 3D Ultra Molecular
Modeling and Analysis Programme [56]. It an interactive

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
93
graphics programme that allows rapid structure building,
geometry optimization with minimum energy and molecu-
lar display. It has ability to handle transition metal
compounds.
state. This is further supported by the presence of a medi-
um band at 1132–1162 cmꢀ1 assignable to m(CAO) (enolic)
[57].
3.2. Characterization dinitrosylmolybdenum(0) complexes
3. Results and discussion
The dinitrosylmolybdenum(0) chelates of 4-aminoanti-
pyrine Schiff bases under this investigation were prepared
according to the reaction Scheme 2.
3.1. Characterization of Schiff base ligand
The pyrazolone based Schiff base ligands in the present
investigation were prepared as shown in Scheme 1.
The resulting compounds are air-stable coloured solids.
Some physical properties of the complexes are given in
Table 2. They were characterized by the following physical
studies.
The formation of the Schiff base ligands is consistent
with the microanalytical data of the ligands. The microan-
alytical data, melting points, colours, % yields and impor-
tant IR spectral bands are given in Table 1. The formation
of Schiff base ligands is supported by the appearance of a
strong band at 1625–1643 cmꢀ1 due to m(C@N) (azome-
thine) in the IR spectra of these ligands [53]. The appear-
ance of a broad band due to m(OH) centred at 3419–3440
suggests that these ligands exist in enol form in the solid
3.3. Infrared spectral studies
The important infrared spectral bands of the complexes
along with their tentative assignments are given in Table 3.
All the ligands used in the present investigation exist in
enol form (vide supra). Hence, they possess seven potential
O
N
O
O
N
O
H2N
N
-H2O
R
N
N
+
N
N
O
N
4-Acyl-3-methyl-1-phenyl-
2-pyrazolin-5-one
4-Aminoantipyrine
R
N
Schiff base ligands
N
O
N
N
O
1
N
5
2
3
4
;
(mphvp-aapH, I)
(bmphp-aapH, II)
R = C4H9
= C6H5;
N
O
N
HO
5
= C2H5;
= CH3;
(mphpp-aapH, III)
(amphp-aapH, IV)
(iso-bumphp, V)
R
N
R
4
1
N
2
3
N
N
= CH(CH3)2
Keto
Enol
Scheme 1. Synthesis of Schiff base ligands.
DMF
(NH4)6Mo7O24.4H2O + NH2OH.HCl (Excess)
7[Mo(NO)2]2+ + other products
5.6 mmol (Green solution)
(1)
(2)
(1.0g; 0.809 mmol)
(1.7g)
90 °C
Ethanol, H2O
[Mo(NO)2]2+ + LH
[Mo(NO)2(L) (OH)] + 2H+
5.6 mmol
5 mmol Reflux, 8-10 h
Where LH = mphvp-aapH (1), bmphp-aapH (2), mphpp-aapH (3), amphp-aapH (4) or
iso-bumphp-aapH (5)
Scheme 2. Synthesis of dinitrosylmolybdenum(0) complexes.

94
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
Table 3
Important IR spectral bands (cmꢀ1) of the synthesized complexes
Compound No. Compound
m(NO)+ m(C@O) (ketonic) m(C@N) (azomethine) m(CAO) (enolic) m(OH)
m(MoANO)
3430 br 625 w
(1)
(2)
(3)
(4)
(5)
[Mo(NO)2(mphvp-aap)(OH)]
1780 s
1655 s
1773 s
1645 s
1774 s
1653 s
1775 s
1650 s
1582 s
1575 s
1575
1605 s
1598 s
1602 s
1604 s
1608 s
1174 m
1164 m
1174 m
1186 m
1165 m
[Mo(NO)2(bmphp-aap)(OH)]
[Mo(NO)2(mphpp-aap)(OH)]
[Mo(NO)2(amphp-aap)(OH)]
3428 br 621 w
3413 br 620 w
3410 br 656 w
3430 br 630 w
1581 s
1584 s
[Mo(NO)2(iso-bumphp-aap)(OH)] 1772 s
1650 s
donor sites: (i) and (ii) the ring nitrogens, N1, (iii) and (iv)
the ring nitrogens, N2, (v) the enolic oxygen of 2-pyrazolin-
5-one skeleton, (vi) the cyclic carbonyl oxygen of 3-pyraz-
olin-5-one skeleton and (vii) azomethine nitrogen. The
coordination of the ring nitrogens N1 is unlikely because
of the presence of a bulky phenyl group attached to it in
2- and 3-pyrazolin-5-one skeletons. Coordination of N1
of 3-pyrazolin-5-one skeleton is also unfavourable due to
the possible Zwitterion [58] formation on account of cyclic
amide group and thereby lowering the basidity of N1 as
shown below in Scheme 3.
Considering the planarity of the ligands, the coordina-
tion of ring nitrogens, N2, is also unlikely due to being
back side of the suitable donor sites (v), (vi), (vii) with ref-
erence to the details of donor sites given above. Moreover,
the coordination of the ring nitrogen N2 of 3-pyrazolin-
5-one skeleton is also unfavourable due to the possible
zwitterion [58] formation on account of conjugation and
thereby lowering the basidity of N2 as shown below in
Scheme 4.
-
.
N
N
.
.
O
O
1
.
1
N
3
+
N
3
2
2
5
5
4
4
N
N
HO
HO
R
5
R
5
4
1
N
4
1
N
2
3
2
3
N
N
Scheme 4. Zwitterion formation due to conjugation in 3-pyrazolin-5-one
skeleton.
dination through carbonyl oxygen. The m(C@O) for the
cyclic carbonyl group at 1666,1670,1669, 1674 and
1670 cmꢀ1 in uncoordinated mphvp-aapH, bmphp-aapH,
mphpp-aapH, amphp-aapH and iso-bumphp-aapH,
respectively, is shifted to lower wave numbers and
appears at 1582, 1575, 1575, 1581 and 1584 cmꢀ1 in
the respective complexes. This indicates that the cyclic
carbonyl oxygen [59] is bonded to molybdenum in these
complexes.
The IR spectra of these ligands exhibit a strong band
at 1630–1643 cmꢀ1 assignable to m(C@N) (azomethine).
In the spectra of the respective complexes this band is
shifted to lower frequency [60] (see Table 3), suggesting
the coordination of the azomethine nitrogen to the metal
centre.
The ring nitrogen N2 in these ligands is found to be inert
towards coordination to molybdenum as revealed by no
change in m(C@N2) (1583–1589 cmꢀ1) of the free ligands
after complexation. In fact, m(C@N2) mode seems to be
merged with m(C@O) (cyclic) mode in the respective
complexes.
For a carbonyl donor, a significant shift of m(C@O)
to lower wave number takes place because of the coor-
In all the complexes, the absence of a broad band cen-
tred at 3419–3440 cmꢀ1 and the presence of a medium
band at 1164–1186 cmꢀ1 due to m(CAO) (enolic) indicate
the deprotonation and coordination of enolic oxygen [53]
to the metal centre.
The appearance of two strong bands in the region
1772–1780 and 1645–1655 cmꢀ1 and a weak band at
620–656 cmꢀ1 may be assigned to m(NO)+ and
m(MoANO), respectively, which are in agreement with
previously reported results [61,62]. The appearance of
two m(NO) bands in the spectra of all the synthesized
complexes suggests the presence of a cis-[Mo(NO)2]2+
moiety [61,63] in the complexes. The appearance of
m(OH) mode at 3410–3430 cmꢀ1 in all the complexes
1
-
.
N
N
.
..2
O
O
+
3
N
N
2
5
3
4
4
N
N
HO
HO
R
5
R
5
4
1
N
4
1
N
2
3
2
3
N
N
Scheme 3. Zwitterion formation due to cyclic amide in 3-pyrazolin-5-one
skeleton.

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
95
under study is most probably due to presence of a coor-
3.4. Conductance measurements
dinated hydroxy group. The IR spectra of a representa-
tive Schiff base ligand, mphpp-aapH (III), and its
complex, [Mo(NO)2(mphpp-aap)(OH)] (3), are given in
Figs. 1 and 2, respectively.
The molar conductances measured in 10ꢀ3 M DMF
solutions of these complexes are in the range 25.3–
45.4 Xꢀ1 cm2 molꢀ1 and thereby indicate the non-electro-
Fig. 1. IR spectrum of mphpp-aapH.
Fig. 2. IR spectrum of [Mo(NO)2(mphpp-aap)(OH)].

96
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
lytic nature of these complexes [64]. The high molar con-
ductance values are most probably due to strong donor
capacity of dimethylformamide, which may lead to the dis-
placement of anionic ligands and change of electrolyte [64]
type.
thermogravimetric analysis in the temperature range
50–1000 ꢁC at the heating rate of 15.8 ꢁC minꢀ1. The
compound (2) shows a weight loss of 2.64% at 146 ꢁC
corresponding to the elimination of one hydroxo group
from the complex (calcd. 2.67%). This compound shows
six more weight losses at different temperatures which we
could not correlate separately. However, the weight loss
observed (83.77%) at ꢁ782 ꢁC corresponds to the elimina-
tion of one hydroxo-, two nitrosyl-, and one ligand-
group(s) against a theoretical weight loss of 84.88%.
The first weight loss of 2.65% displayed by the com-
pound (3) at 150 ꢁC corresponds to the elimination of
one hydroxo group from the complex (calcd. 2.89%). Sim-
ilar to compound (2), this compound also exhibits six more
weight losses, which we again could not correlate separate-
ly. However, the weight loss observed (83.5%) at ꢁ715 ꢁC
corresponds to the elimination of one hydroxo-, two nitro-
syl-, and one ligand-group(s) from the complex (calcd.
83.65%). The thermograms of these two compounds,
therefore, corroborate some of the assumptions made on
the basis of infrared spectral studies for these complexes
(vide supra).
3.5. Magnetic measurements
The magnetic susceptibility measurements of these com-
plexes indicate that they are diamagnetic and, hence, they
should have ground states with a molecular orbital config-
uration (1a2)2 (1a1)2 and (1b2)2 following the molecular
orbital diagram reported elsewhere [4]. This result is consis-
tent with the low-spin {Mo(NO)2}6 electron configuration
of Mo(0) in these complexes. The diamagnetic and non-
electrolytic nature of these complexes also supports the
presence of two NO+ groupings in all of these complexes.
3.6. Thermogravimetric analyses
Two compounds, namely, [Mo(NO)2(bmphp-aap)(OH)]
(2) and [Mo(NO)2(mphpp-aap)(OH)] (3), were subjected to
Table 4
Electronic spectral data of some complexes
Compound No.
Compound
kMax (nm)
e (L molꢀ1 cmꢀ1
)
Peak assignment
(1)
[Mo(NO)2(mphvp-aap)(OH)]
298
338
365
393
417
720
289
313
339
357
416
295
316
351
365
457
293
329
356
387
444
705
274
296
325
349
440
280
325
475
650
296
433
655
5265
5520
5914
3747
3634
745
1b2 fi 2b1
1b2 fi 2a2
1b2 fi 3a1
1b2 fi 2b2
1b2 fi 1b1
1b2 fi 2a1
(2)
(3)
(4)
[Mo(NO)2(bmphp-aap)(OH)]
[Mo(NO)2(mphpp-aap)(OH)]
[Mo(NO)2(amphp-aap)(OH)]
4390
4315
5221
5409
3052
4411
4666
5141
5054
3480
4110
5255
5046
3021
2722
166
3722
4312
4582
4821
1942
10,798
2264
2667
179
1b2 fi 2a2
1b2 fi 3a1
1b2 fi 2b2
1b2 fi 1b1
1b2 fi 2a1
1b2 fi 2a2
1b2 fi 3a1
1b2 fi 2b2
1b2 fi 1b1
1b2 fi 2a1
1b2 fi 2b1
1b2 fi 2a2
1b2 fi 3a1
1b2 fi 2b2
1b2 fi 1b1
1b2 fi 2a1
(5)
[Mo(NO)2(iso-bumphp-aap)(OH)]
1b2 fi 2a2
1b2 fi 3a1
1b2 fi 2b2
1b2 fi 1b1
1b2 fi 2a1
Ref. 43
Ref. 43
Mo(NO)2(o-AP)2
p* (NO) ‹ M charge transfer
p* (NO) ‹ M charge transfer
d ‹ d
d ‹ d
[Mo(NO)2(2-pic)2]
5372
433
296
p* (NO) ‹ M charge transfer
p* (NO) ‹ M charge transfer
d ‹ d

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
97
3.7. Electronic spectral studies
3.8. 3D molecular modeling and analysis
Electronic spectra of complexes were recorded in
10ꢀ3 M DMF solutions. The electronic spectral peaks
observed in each of the complexes along with their molar
extinction coefficients are presented in Table 4. The com-
pounds 1 and 6 in the present investigation display six tran-
sitions while compounds 2, 3 and 5 exhibit only five
transitions. The assignments of these transitions are given
in Table 4, and are based on molecular orbital diagram
applicable to hexa-coordinated dinitrosyl complexes
reported elsewhere [4]. These observations are in agreement
with the results reported by Perpinan et al. [44], for some
dinitrosylmolybdenum(0) complexes.
In view of the hexa-coordination of the present com-
plexes (vide infra, Section 4), the molecular modeling
of compound, [Mo(NO)2(bmphp-aap)(OH)] (2) as a rep-
resentative, is based on its octahedral structure. The
details of bond lengths and bond angles as per the 3D
structure (Fig. 3) are given in Tables 5 and 6, respective-
ly. For convenience of looking over the different bond
lengths and bond angles, the various atoms in the com-
pound in question are numbered in arabic numerals. In
all, 198 measurements of the bond lengths (72 in num-
bers), plus the bond angles (126 in numbers) are listed
in Tables 5 and 6. Except few cases, optimal values of
Fig. 3. 3D structure of [Mo(NO)2(bmphp-aap)(OH)] (2).

98
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
Table 5
Table 5 (continued)
Various bond lengths of compound [Mo(NO)2(bmphp-aap)(OH)] (2)
S. No.
Atoms
Actual bond length
1.6235
Optimal bond length
S. No.
Atoms
Actual bond length
Optimal bond length
66
67
68
69
70
71
72
N(4)AN(5)
Mo(24)AO(3) 1.94
–
–
1
2
3
4
5
6
7
8
9
O(41)AN(40)
C(39)AH(66)
C(39)AC(38)
H(65)AC(37)
C(38)AC(37)
H(64)AC(36)
C(37)AC(36)
C(35)AH(63)
C(35)AC(36)
H(62)AC(34)
C(39)AC(34)
C(35)AC(34)
C(33)AH(61)
C(32)AH(60)
C(33)AC(32)
H(59)AC(31)
C(32)AC(31)
H(58)AC(30)
C(30)AC(31)
C(29)AH(57)
C(29)AC(30)
C(33)AC(28)
C(29)AC(28)
H(56)AO(27)
N(26)AO(25)
Mo(24)AN(40)
N(26)AMo(24)
Mo(24)AO(27)
C(23)AC(28)
H(54)AC(22)
C(22)AH(55)
H(53)AC(22)
Mo(24)AO(21)
C(20)AO(21)
C(19)AC(23)
C(19)AC(20)
C(22)AC(18)
C(19)AC(18)
C(18)AN(17)
C(38)AN(16)
C(20)AN(16)
N(17)AN(16)
N(15)AMo(24)
N(15)AC(23)
C(14)AH(52)
H(51)AC(13)
C(14)AC(13)
C(12)AH(50)
C(13)AC(12)
C(11)AH(49)
C(11)AC(12)
C(10)AH(48)
C(10)AC(11)
C(9)AC(14)
1.1318
1.1
1.337
1.1
1.337
1.1
1.337
1.1
1.337
1.1
1.337
1.337
1.1
1.1
1.337
1.1
–
1.1
1.42
1.1
1.42
1.1
1.42
1.1
1.42
1.1
1.42
1.42
1.1
1.1
1.42
1.1
1.42
1.1
1.42
1.1
1.42
1.42
1.42
0.942
–
N(4)AC(2)
C(2)AO(3)
C(1)AN(15)
C(1)AC(7)
C(1)AC(2)
1.266
2.8446
1.266
1.337
1.337
1.462
1.355
1.462
1.337
1.503
Table 6
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
Various bond angles of compound [Mo(NO)2(bmphp-aap)(OH)] (2)
S. No.
Atoms
Actual bond
angles
Optimal bond
angles
1
2
3
4
5
6
7
8
9
H(64)AC(36)AC(37)
H(64)AC(36)AC(35)
C(35)AC(36)AC(37)
H(63)AC(35)AC(36)
H(63)AC(35)AC(34)
C(36)AC(35)AC(34)
C(39)AC(34)AH(62)
C(35)AC(34)AH(62)
C(39)AC(34)AC(35)
C(38)AC(39)AH(66)
H(66)AC(39)AC(34)
C(38)AC(39)AC(34)
H(65)AC(37)AC(38)
H(65)AC(37)AC(36)
C(38)AC(37)AC(36)
C(33)AC(32)AH(60)
H(60)AC(32)AC(31)
C(33)AC(32)AC(31)
H(59)AC(31)AC(32)
H(59)AC(31)AC(30)
C(32)AC(31)AC(30)
H(58)AC(30)AC(31)
C(29)AC(30)AH(58)
C(29)AC(30)AC(31)
C(32)AC(33)AH(61)
H(61)AC(33)AC(28)
C(32)AC(33)AC(28)
H(57)AC(29)AC(30)
H(57)AC(29)AC(28)
C(30)AC(29)AC(28)
C(39)AC(38)AC(37)
C(39)AC(38)AN(16)
C(37)AC(38)AN(16)
H(54)AC(22)AH(55)
H(54)AC(22)AH(53)
H(54)AC(22)AC(18)
H(53)AC(22)AH(55)
C(18)AC(22)AH(55)
H(53)AC(22)AC(18)
C(18)AN(17)AN(16)
C(38)AN(16)AC(20)
C(38)AN(16)AN(17)
C(20)AN(16)AN(17)
C(19)AC(20)AO(21)
O(21)AC(20)AN(16)
C(19)AC(20)AN(16)
C(22)AC(18)AC(19)
C(22)AC(18)AN(17)
C(19)AC(18)AN(17)
H(51)AC(13)AC(14)
H(51)AC(13)AC(12)
C(14)AC(13)AC(12)
120.0001
119.9998
120.0001
120.0006
119.9995
119.9999
120.0001
120.0001
119.9998
120
119.9998
120.0002
120.0001
119.9997
120.0001
120.0003
119.9997
120
120
120
–
120
120
–
120
120
–
120
120
–
120
120
–
120
120
–
120
120
–
120
120
–
1.337
1.1
1.337
1.1
1.337
1.337
1.337
0.942
1.1318
1.976
1.976
1.94
1.337
1.113
1.113
1.113
1.1464
1.355
1.337
1.337
1.497
1.337
1.26
1.266
1.266
1.614
1.976
1.266
1.1
1.1
1.337
1.1
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
–
–
–
1.503
1.113
1.113
1.113
–
1.355
1.503
1.337
1.497
1.503
1.26
1.462
1.462
1.426
–
1.266
1.1
1.1
1.42
1.1
1.42
1.1
120.0005
119.9995
120
120.0001
120
119.9999
120.0002
119.9994
120.0003
119.9999
120.0002
120
119.9999
119.9999
120.0002
109.5201
109.4417
109.4415
109.4618
109.4621
109.5001
103.7077
128.353
128.3535
103.2934
124.298
124.6986
110.9999
124.5
120
120
–
120
120
–
120
120
120
109
109
110
109
110
110
115
124
124
124
124.3
–
120
121.4
115.1
120
120
120
–
1.337
1.1
1.337
1.1
1.42
1.1
1.337
1.337
1.337
1.113
1.113
1.113
1.497
1.113
1.113
1.113
1.47
1.42
1.42
1.42
1.113
1.113
1.113
1.497
1.113
1.113
1.113
1.47
1.462
1.462
C(10)AC(9)
C(8)AH(47)
C(8)AH(46)
C(8)AH(45)
C(8)AC(7)
C(6)AH(42)
H(44)AC(6)
C(6)AH(43)
N(5)AC(6)
124.5002
110.9998
120.0002
120.0002
119.9996
N(5)AC(7)
N(4)AC(9)
1.266
1.266

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
99
Table 6 (continued)
Table 6 (continued)
S. No.
Atoms
Actual bond
angles
Optimal bond
angles
S. No.
Atoms
Actual bond
angles
Optimal bond
angles
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
C(13)AC(12)AH(50)
C(11)AC(12)AH(50)
C(11)AC(12)AC(13)
H(49)AC(11)AC(12)
C(10)AC(11)AH(49)
C(10)AC(11)AC(12)
C(13)AC(14)AH(52)
C(9)AC(14)AH(52)
C(9)AC(14)AC(13)
C(11)AC(10)AH(48)
H(48)AC(10)AC(9)
C(11)AC(10)AC(9)
O(41)AN(40)AMo(24)
H(56)AO(27)AMo(24)
Mo(24)AN(26)AO(25)
C(33)AC(28)AC(29)
C(33)AC(28)AC(23)
C(29)AC(28)AC(23)
C(20)AC(19)AC(23)
C(18)AC(19)AC(23)
C(18)AC(19)AC(20)
C(19)AC(23)AC(28)
N(15)AC(23)AC(28)
C(19)AC(23)AN(15)
Mo(24)AO(21)AC(20)
C(10)AC(9)AC(14)
N(4)AC(9)AC(14)
119.9996
120.0002
120.0001
120.0001
119.9996
120.0003
120.0001
119.9998
120.0001
119.9999
120.0005
119.9996
120.0001
120
119.9998
119.9998
120.0007
119.9995
120
128.9983
110.9992
119.9996
120
120.0004
137.6547
120.0002
120
119.9998
109.4622
109.4417
109.4996
109.5205
109.4617
109.4416
109.52
109.4618
109.4619
109.4415
109.4421
109.4999
128.3983
128.3979
103.2038
119.9983
111
128.9982
124.4998
124.4999
111.0003
154.3341
64.3341
97.4958
69.1324
158.5672
90
120
120
–
120
120
–
120
120
–
120
120
–
117
118
119
120
121
122
123
124
125
126
N(5)AN(4)AC(9)
C(9)AN(4)AC(2)
N(5)AN(4)AC(2)
Mo(24)AO(3)AC(2)
N(4)AC(2)AO(3)
N(4)AC(2)AC(1)
C(1)AC(2)AO(3)
N(15)AC(1)AC(7)
N(15)AC(1)AC(2)
C(7)AC(1)AC(2)
128.5478
128.5474
102.9047
69.2419
120.0003
110.9995
99.0816
119.9999
110.9998
111.0001
–
124
–
–
–
120
124.3
120
120
120
–
–
–
both the bond lengths and the bond angles are given in
the tables along with the actual ones. The actual bond
lengths/bond angles given in Tables 5/6 are calculated
values as a result of energy optimization in CHEM 3D
Ultra, while the optimal bond length/optimal bond angle
values are the most desirable/favourable (standard) bond
lengths/bond angles established by the builder unit of the
CHEM 3D. The missing of some values of standard
bond lengths/bond angles may be due to the limitations
of the software, which we had already noticed in
modeling of other systems [65,66]. In most of the cases,
the actual bond lengths and bond angles are close to
the optimal values, and thus the proposed structures of
the compound (2) as well as of the others are acceptable
[65,66].
120
120
120
120
120
120
120
120
120
–
120
120
120
109
109
–
N(4)AC(9)AC(10)
H(44)AC(6)AH(42)
H(42)AC(6)AH(43)
N(5)AC(6)AH(42)
H(44)AC(6)AH(43)
H(44)AC(6)AN(5)
N(5)AC(6)AH(43)
H(47)AC(8)AH(46)
H(45)AC(8)AH(47)
H(47)AC(8)AC(7)
H(45)AC(8)AH(46)
C(7)AC(8)AH(46)
H(45)AC(8)AC(7)
C(6)AN(5)AC(7)
N(4)AN(5)AC(6)
109
–
–
4. Conclusions
The satisfactory analytical data and all of the
physico-chemical evidence presented above suggest that
the present complexes are of the composition,
[Mo(NO)2(L)(OH)], {where LH = N-(30-methyl-10-phen-
yl-40-valerylidene-20-pyr azolin-50-one)-4-aminoantipyrine
(mphvp-aapH), N-(40-benzoylidene-30-methyl-10-phenyl-
20-pyr azolin-50-one)-4-aminoantipyrine (bmphp-aapH),
109
109
110
109
110
110
108
–
N(4)AN(5)AC(7)
–
–
–
Mo(24)AN(15)AC(23)
C(1)AN(15)AMo(24)
C(1)AN(15)AC(23)
C(8)AC(7)AN(5)
C(1)AC(7)AC(8)
C(1)AC(7)AN(5)
124
125.3
121.4
120
–
–
–
–
–
–
–
–
–
–
–
–
–
N
NO
O
N
ON
OH
N(26)AMo(24)AN(40)
O(27)AMo(24)AN(40)
O(21)AMo(24)AN(40)
N(15)AMo(24)AN(40)
O(3)AMo(24)AN(40)
N(26)AMo(24)AO(27)
N(26)AMo(24)AO(21)
N(26)AMo(24)AN(15)
N(26)AMo(24)AO(3)
O(27)AMo(24)AO(21)
N(15)AMo(24)AO(27)
O(27)AMo(24)AO(3)
N(15)AMo(24)AO(21)
O(3)AMo(24)AO(21)
N(15)AMo(24)AO(3)
Mo
O
N
N
N
R
90.0001
134.2012
44.7555
107.5296
128.9336
132.1742
98.0308
90
(1)
(2)
R = C4H9;
= C6H5;
= C2H5;
= CH3;
(3)
(4)
(5)
= CH(CH3)2
–
–
90.0002
Fig. 4. Proposed structure of complexes.

100
R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
N-(30-methyl-10-phenyl-40-propionylidene-20-pyr azolin-50-
one)-4-aminoantipyrine (mphpp-aapH), N-(40-acetylid-
ene-30-methyl-10-phenyl-20-pyr azolin-50-one)-4-aminoan-
tipyrine (amphp-aapH) or N-(-40-iso-butyrylidene-30-
methyl-10-phenyl-20-pyra zolin-50-one)-4-aminoantipyrine
(iso-bumphp-aapH), As these complexes display two
peaks for mNO+ mode, a cis-octahedral structure shown
in Fig. 4 has been proposed for these complexes.
[20] R.C. Maurya, A.K. Singh, Indian J. Chem. 43A (2004) 551.
[21] L. Andrews, A. Citra, Chem. Rev. 102 (2002) 885.
[22] A.A. Levin, J. Mol. Struct. 272 (1992) 133.
[23] O.V. Sizova, V.I. Baranovski, N.V. Ivanova, V.V. Sizova, Mol. Phys.
101 (2003) 715.
[24] D. Chatterjee, A. Mitra, R.E. Shepherd, R.F. Furchgott, Inorg.
Chim. Acta 357 (2004) 980.
[25] A. Katho, Z. Opre, L. Gabor, J. Ferenc, G. Lawrency, T. Goo, J.
Mol. Cat. A: Chem. 204–205 (2003) 143.
[26] D.P.S. Mingos, D.J. Sherman, in: A.J. Sykes (Ed.), Advances in
Inorganic Chemistry, vol. 4, Harcourt, Brace and Jovanovich,
London, 1989, pp. 293–377.
Acknowledgements
[27] A. Miyata, M. Murakami, R. Irie, T. Katsuki, Tetrahedron Lett. 42
(2001) 7067.
[28] W. Odenkirk, A.L. Rheingold, B. Bosnich, J. Am. Chem. Soc. 114
(1992) 6392.
[29] K.K. Pandey, Coord. Chem. Rev. 51 (1983) 69, and references
therein.
[30] R.F. Furchgott, in: C. Owman, J.E. Hardebo (Eds.), Neural
Regulation of Brain Circulation, Elsevier, New York, 1986, p. 3.
[31] R.F. Furchgott, Ann. Rev. Pharmacol. Toxicol. 35 (1995) 1.
[32] R.F. Furchgott, Angew. Chem., Int. Ed. 38 (1999) 1870.
[33] L.J. Ignarro, Nitric Oxide Biology and Pathology, Academic Press,
New York, 2000.
[34] V. Tognido, R.S. da Silva, A.C. Tedesco, Inorg. Chim. Acta 316
(2001) 7, and references therein.
[35] C.F. Fortney, S.J. Geib, F. Lin, R.E. Shepherd, Inorg. Chim. Acta 10
(2004) 2921.
The authors are thankful to Dr. S.M. Paul Khurana,
Vice-chancellor of this University, for encouragement,
and Professor K.K. Verma, Head, Department of
Chemistry, for laboratory facilities and helpful
discussion. Analytical facilities provided by the Central
Drug Research Institute, Lucknow, India, and the
Regional Sophisticated Instrumentation Centre, Indian
Institute of Technology, Chennai, India, are gratefully
acknowledged.
References
[1] N. Raman, A. Kulandaisamy, K. Jeyasubramanian, Indian J. Chem.
41 (2002) 942.
[2] M. Windholz (Ed.), The Merck Index, Encyclopedia of Chemicals,
Drugs and Biologicals, Merck and Co., Inc., Rahway, New Jersey,
USA, 1983.
[3] J.H. Enemark, R.D. Feltham, Coord. Chem. Rev. 13 (1974) 339.
[4] J.H. Enemark, R.D. Feltham, in: G. Geoffroy (Ed.), Topics in
Inorganic and Organometallic Stereochemistry, vol. 12, Wiley, New
York, 1981, pp. 152–215.
[5] B.L. Westcott, J.H. Enemark, in: E.I. Solomon, A.B.P. Lever (Eds.),
Inorganic Electronic Spectroscopy, vol. II, Wiley, New York, 1999,
pp. 403–450.
[6] R.C. Maurya, Synthesis and Characterization of Some Novel
Nitrosyl Compounds, first ed., Pioneer Publications, Jabalpur, 2000.
[7] G.B. Richter-Addo, P. Legzdins, Metal Nitrosyl, Oxford University
Press, New York, 1992.
[8] T. Hirano, T. Oi, H. Nagao, K. Morokuma, Inorg. Chem. 42 (2003)
6575.
[9] B.J. Coe, S.J. Glenwright, Coord. Chem. Rev. 203 (2000) 5, and
references therein.
[10] T.W. Hayton, P. Legzdins, W. Brett Sharp, Chem. Rev. 102 (2002)
935–991, and references therein.
[36] E.A. Zuech, J. Chem. Soc., Chem. Commun. (1968) 1892.
[37] E.A. Zuech, W.B. Hyghes, D.H. Kubicek, E.T. Kittleman, J. Am.
Chem. Soc. 92 (1970) 528.
[38] W.B. Hughes, Inorg. Chem. 13 (1974) 1531.
[39] A. Keller, R. Matusiak, J. Mol. Cat. A: Chem. 142 (1999) 317.
[40] D. Ballivet-Tkachenko, C. Bremard, F. Abraham, G. Nowogrocki, J.
Chem. Soc. Dalton Trans. (1983) 1137.
[41] M. Green, S.H. Taylor, J. Chem. Soc. Dalton Trans. (1973) 2629.
[42] K. Bencze, J. Kohan, B. Mohai, L. Marko, J. Organomet. Chem. 70
(1974) 421.
[43] S. Sarkar, P. Subramanian, Inorg. Chim. Acta 35 (1979) 357.
[44] M.F. Perpinan, L. Ballester, A. Santos, A. Monge, C. Ruiz-Valero,
E.G. Puebla, Polyhedron 6 (1987) 1523.
[45] T.K. Banerjee, S.K. Brahma, S.P. Bag, Indian J. Chem. 30A (1991)
281.
[46] R.C. Maurya, D.D. Mishra, S. Mukherjee, P.K. Trivedi, S.K.
Jaiswal, Synth. React. Inorg. Met.-Org. Chem. 23 (1993) 723.
[47] R.C. Maurya, D.D. Mishra, S. Mukherjee, S.K. Jaiswal, Synth.
React. Inorg. Met.-Org. Chem. 23 (1993) 1073.
[48] R.C. Maurya, D.D. Mishra, S. Mukherjee, S.K. Jaiswal, Synth.
React. Inorg. Met.-Org. Chem. 24 (1994) 53.
[49] R.C. Maurya, M.R. Maurya, S. Gopinathan, C. Gopinathan,
Polyhedron 12 (1993) 159.
[11] T. Kimura, T. Sakurai, T. Shima, M. Togano, M. Mukaida, T.
Nomura, Inorg. Chim. Acta 69 (1983) 135.
[12] E. Miki, K. Harada, Y. Kamata, M. Umehara, K. Mizumachi, M.
Tanaka, T. Nagai, T. Ishimori, M. Nakahara, Polyhedron 10 (1991)
583.
[50] R.C. Maurya, D.D. Mishra, N.S. Rao, N.N. Rao, Polyhedron 13
(1994) 2653.
[51] R.C. Maurya, A. Pandey, T. Singh, Synth. React. Inrog. Met.-Org.
Chem. 32 (2002) 247.
[13] H. Nishimura, H. Matsuzawa, T. Togano, M. Mukaida, H. Kakih-
ana, F. Bottomly, J. Chem. Soc. Dalton Trans. (1991) 137.
[14] H. Tomizawa, E. Miki, K. Mizumachi, T. Ishimori, Bull. Chem. Soc.
Japan 67 (1994) 1816.
[15] R.C. Maurya, D.D. Mishra, S. Mukherjee, J. Dubey, Polyhedron 14
(1995) 1351.
[16] R.C. Maurya, R. Verma, Indian J. Chem. 37A (1998) 147.
[17] R.C. Maurya, V. Pillai, S. Rajput, Synth. React. Inorg. Met.-Org.
Chem. 33 (2003) 699.
[52] B.S. Jensen, Acta Chim. Scand. 13 (1959) 1668.
[53] R.C. Maurya, D.D. Mishra, N.S. Rao, N.N. Rao, Bull. Chem. Soc.
Japan 68 (1995) 1592.
[54] A.I. Vogel, Text book of Quantitative Inorganic Analysis, E.L.B.S,
1978, p. 471.
[55] G. Svehla, Vogel’s Qualitative Inorganic Analysis, sixth ed., Orient
Longman Limited, UK, 1987, p. 163.
[56] CS Chem 3D Ultra Molecular Modeling and Analysis, Cambridge;
<www.cambridgesoft.com>.
[18] R.C. Maurya, D. Sutradhar, S. Rajput, Synth. React. Inrog.
Met.-Org. Chem. 33 (2003) 291.
[57] R.C. Maurya, D.D. Mishra, N.S. Rao, M.N. Jayaswal, N.N. Rao,
Polyhedron 12 (1993) 2045.
[19] R.C. Maurya, H. Singh, D. Sutradhar, Synth. React. Inrog.
Met.-Org. Chem. 33 (2003) 581.
[58] R.C. Maurya, T. Singh, B. Shukla, J. Dube, G.P. Shukla, Synth.
React. Inorg. Met.-Org. Chem. 27 (1997) 1467.

R.C. Maurya et al. / Journal of Molecular Structure 798 (2006) 89–101
101
[59] R.C. Maurya, D.D. Mishra, S. Mukherjee, P.K. Trivedi, Transit.
Metal Chem. 16 (1991) 524.
[60] R.C. Maurya, D.D. Mishra, N.S. Rao, N.N. Rao, Shukla, Synth.
React. Inorg. Met.-Org. Chem. 24 (1994) 1013.
[61] R.C. Maurya, J. Dubey, B. Shukla, Synth. React. Inorg. Met.-Org.
Chem. 28 (1998) 1159.
[62] R.C. Maurya, V. Pillai, Indian J. Chem. 38A (1999) 736.
[63] S. Sarkar, R.C. Maurya, S.C. Chaurasia, Transit. Metal Chem. 1
(1976) 49.
[64] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[65] R.C. Maurya, S. Rajput, J. Mol. Struct. 687 (2004) 35.
[66] R.C. Maurya, S. Rajput, J. Mol. Struct. (in press).